1. Field of the Invention
Vanes for rotating heat engines such as steam turbines, gas turbines, turbocompressors, etc. and their effective protection against attacks during operation such as oxidation, corrosion, wear and damage.
The invention relates to the improvement of the resistance to corrosion and erosion of vanes of rotating heat engines by further developing the process for applying suitable protective layers.
In particular, the invention concerns a process for increasing the resistance to corrosion and erosion of a vane of a rotating heat engine, which vane consists essentially of a ferritic and/or ferritic-martensitic base material, by applying a firmly adhering protective surface layer.
2. Discussion of Background
In order to be able to satisfy the numerous demands, the vanes of rotating heat engines are often provided with protective layers. Use is made of these both in the case of steam turbine vanes and gas turbine vanes and also in the case of compressor vanes. The aim, above all, is to increase the resistance to corrosion and oxidizing attack, and also to erosion and wear. Among the materials employed for protective layers, the elements of Cr, Al, Si, which form oxidic top layers, assume a special position. Layers which have a high Al content are employed inter alia as filler for carbide-containing coatings (Cr.sub.2 C.sub.3 ; WC) in engine manufacturing.
The following publications on the prior art may be specified:
F. N. Davis, C. E. Grinnell, "Engine Experience of Turbine Rotor Blade Materials and Coatings", The American Society of Mechanical Engineers, 345 E. 47 St. New York, N.Y. 10017, 82-GT-244 PA1 SermeTel Technische Information (SermeTel Technical Information): "SermaLoy J-Prozess STS" (SermeLoy J-Process STS), SermeTel GmbH, Weilenburgstrasse 49, D-5628 Heiligenhaus, Federal Republic of Germany PA1 Mark F. Mosser and Bruce G. McMordie, "Evaluation of Aluminium/Ceramic Coating on Fasteners to Eliminate Galvanic Corrosion", Reprinted from. SP-649-Corrosion: Coatings and Steels, International Congress and Exposition, Detroit, Michigan, Feb. 24-28, 1986, ISSN 0148-7191, Copyright 1986 Society of Automotive Engineers, Inc. PA1 Thomas F. Lewis III, "Gator-Gard, The Process, Coatings, and Turbomachinery Applications", Presented at the International Gas Turbine Conference and Exhibit, Dusseldorf, West Germany - Jun. 8-12, 1986, The American Society of Mechanical Engineers, 345 E. 47 St., New York, N.Y. 10017, 86-GT-306 PA1 H. J. Kolkman, "New Erosion Resistant Compressor Coatings", Presented at the Gas Turbine and Aeroengine Congress, Amsterdam, The Netherlands - Jun. 6-9, 1988, The American Society of Mechanical Engineers, 345 E. 47 St., New York, N.Y. 10017, 88-GT-186.